1. Field of the Invention
The present invention is related to molding materials consisting of a thermotropic, aromatic polyester.
2. Discussion of the Background
Thermotropic, aromatic polyesters comprising terephthalic acid, isophthalic acid, p-hydroxybenzoic acid and bisphenols are known (DE-OS No. 20 25 971). The melting points of the polyesters described in this reference are generally above 300.degree. C., and may be even above 400.degree. C. Such polyesters cannot be readily processed.
In addition to prior known initial monomers, polyesters with improved processability comprise e.g. benzophenonedicarboxylic acid (DE-OS No. 34 27 886) or dihydroxybenzophenone (DE-OS No. 34 15 530). However, the thermal stability of the molding materials prepared according to these references is not satisfactory.
Polyesters, which contain sulfone group-containing starting materials, are known from EP-PS No. 0 081 900. However, the patent specification discloses such a broad range of these starting materials that it is impossible to recognize especially advantageous proportions of the materials. Moreover, DE-OS No. 35 42 778 describes fully aromatic, mesomorphic polyether esters in which, among others, 4,4'-di(p-hydroxyphenoxy)-diphenylsulfone was used as monomer, but which cannot be obtained free of oligomers.
A need continues to exist for readily processable, aromatic polyesters having high chemical resistance.